(a) Technical Field
The present invention relates to a method of manufacturing a silicon carbide (SiC) Schottky barrier diode (SBD). More particularly, it relates to a method of manufacturing a SiC Schottky barrier diode with an improved breakdown voltage.
(b) Background Art
A Schottky diode is a special type of diode formed by the junction between an n-type semiconductor and a metal, which is named after the German physicist, Walter H. Schottky, who discovered the Schottky barrier.
A Schottky diode has a low forward voltage drop of about 0.2V to about 0.4V, and a switching speed that is 10 times faster than that of a typical diode. A low forward voltage drop produces a low heating value, better power efficiency, and low distortion of an input signal in terms of signal rectification and switching. Fast switching speed correlates to a short recovery time, which relates to how quickly a signal is sent in a forward direction when changing from reverse bias to forward bias.
Accordingly, since Schottky diodes can increase efficiency, they are widely used in fields that require faster switches/rectifiers such as, for example, high-frequency signal processing or power source circuits.
A disadvantage of a Schottky diode is that an electrical field is concentrated at the edge portion of an electrode; consequently, it is not possible to obtain a withstanding voltage as high as the theoretical yield value predicted for a silicon carbide (SiC) device.
Several methods have been attempted to address this disadvantage, including: a field plate structure in which an insulation film such as an oxide is used at the termination of the electrode, a field limiting ring structure that disperses a concentrated electric field, or a junction termination extension structure, all of which may be applied to mitigate the electric field crowding and achieve a device breakdown voltage value closer to the theoretical yield value. Of these methods, the field plate structure has been most widely used as a termination structure for improving the device breakdown voltage because it is simple and inexpensive to manufacture.
In order to use a field plate structure successfully, it is important to form a high quality oxide film having a sufficient thickness. Two methods may be used to produce such an oxide film: high-temperature thermal oxidation and chemical-vapor deposition (CVD). When high-temperature thermal oxidation is used to form an oxide film, the growth rate of the oxide film may be slow, making it difficult to form an oxide film of sufficient thickness. As a result of this limitation, the CVD process is generally used to form a thick oxide film. Unfortunately, the CVD process produces an oxide film having a lower film quality than an oxide film formed by thermal oxidation, which results in a diode with poor breakdown characteristics, and significant current leakage current, making it difficult to manufacture a commercially viable Schottky Barrier Diode (SBD) device using the field plate structure.
In view of the foregoing, there is a need for a technology that will facilitate production of a commercially viable Schottky Barrier Diode for power applications.